An important goal of the hard disk drive industry is to develop magnetic heads with continued increases in disk drive capacity and performance, and continued decreases in the cost of disk drives. Improvements in magnetic heads are sought that provide ever faster data writing speeds, and that allow data to be written with ever increasing data density, that is, with more data stored per unit of disk area.
Typically while a disk drive is operating, the magnetic head is separated from the surface of the disk by a small gap, which is termed the air bearing gap. The air bearing gap is maintained by a slider and a suspension system. The slider includes the magnetic head and an air bearing surface (ABS) that is shaped such that the rotation of the disk past the slider creates an aerodynamic force that tends to push the slider away from the disk. At the same time, the slider is pushed towards the disk by the suspension. The net effect is to maintain a generally uniform distance between the disk and the air bearing surface.
The size of the air bearing gap, also known as the air bearing fly height, is a key parameter of the disk drive. Smaller air bearing gaps allow magnetic heads to have faster writing speeds and higher data density. On the other hand when the gap becomes too small, it becomes too likely that the magnetic head may come into contact with the disk surface, which can permanently damage the magnetic head, the disk surface, or both.
A known problem with magnetic heads is that heat causes uneven thermal expansion of components within the head, thus distorting the air bearing surface of the head. The distortion takes the form of a protrusion of part of the magnetic head into the air bearing gap, where the size of the protrusion can be on the order of 20% of the height of the air bearing gap. The protrusion can contribute to unwanted contact of the magnetic head with the surface of the disk, which can damage the head, the disk, or both.